In recent years, processing techniques for increasing density and micronization are becoming ever more important in manufacturing steps for semiconductor elements. One such machining technique, CMP (chemical mechanical polishing) technique, has become an essential technique in manufacturing steps for semiconductor elements, for STI formation, flattening of pre-metal insulating materials or interlayer insulating materials, and formation of plugs or embedded metal wirings, and the like.
Most commonly used as CMP polishing agents are silica-based CMP polishing agents containing silica (silicon oxide) particles such as fumed silica and colloidal silica as abrasive grains. Silica-based CMP polishing agents have a feature of high flexibility of use, and appropriate selection of the abrasive grain content, pH and additives allows polishing of a wide variety of materials regardless of the insulating material or the conductive material.
Demand is also increasing for CMP polishing agents comprising cerium compound particles as abrasive grains, mainly designed for polishing of insulating materials such as silicon oxide. For example, cerium oxide-based CMP polishing agents comprising cerium oxide (ceria) particles as abrasive grains allow the polishing of silicon oxide at high rate, with even lower abrasive grain contents than silica-based CM′ polishing agents (see Patent Literatures 1 and 2, for example).
Recently, as demand increases for achieving greater micronization of wirings in manufacturing steps for semiconductor elements, generation of polishing scratches during polishing are becoming problematic. Specifically, even when fine polishing scratches generates during the polishing using conventional cerium oxide-based polishing agents, it was not problematic so long as the sizes of the polishing scratches are smaller than conventional wiring widths, but it can be problematic even when the polishing scratches are fine for achieving further greater micronization of wirings.
A solution to this problem is being sought through studying polishing agents that employ particles of hydroxides of a tetravalent metal element (see Patent Literature 3, for example). Methods for producing particles of hydroxides of a tetravalent metal element are also being studied (see Patent Literature 4, for example) Such techniques are aimed at reducing particle-induced polishing scratches, by maintaining the chemical action of particles of the hydroxide of a tetravalent metal element while minimizing their mechanical action.